Phase Transformations and Properties of Silicon and Germanium Under High Pressure

High-pressure studies of silicon and germanium reveal a rich landscape of structural rearrangements that profoundly alter their electronic, optical and mechanical properties. Under compression, the ambient diamond-cubic lattice transforms into a sequence of denser polymorphs—β-tin, simple hexagonal, BC8/R8 and other exotic phases—each offering distinct coordination environments and band-structure characteristics. Decompression and non-equilibrium pathways yield metastable forms that can retain novel properties at ambient conditions. These transformations underpin advances in superconductivity, nano-device engineering and planetary materials science. The ability to manipulate phase stability and kinetics through pressure, strain rate and temperature opens routes to tailored semiconductors, energy-conversion materials and fundamental insights into deformation mechanisms in non-metallic systems.

Research from Nature Portfolio

Recent studies have employed sub-picosecond, highly monochromatic x-ray diffraction to capture the deformation of silicon under laser-driven shock compression. These experiments provide direct evidence that shear stress is relieved via a rapid phase transition from the diamond-cubic structure to high-pressure allotropes, resolving long-standing questions about strain-rate-dependent plasticity in a non-metallic material. A foundational investigation using ultrafast laser-induced confined microexplosions generated six previously unobserved metastable silicon phases, including tetragonal and monoclinic structures. Retained within the parent crystal, these new allotropes exhibit electronic and optical features unattainable through equilibrium synthesis, pointing to transformative applications in photonics and quantum materials.

Phase Transformations and Properties of Silicon and Germanium Under High Pressure publication trend

The graph below shows the total number of articles in phase transformations and properties of silicon and germanium under high pressure across all publications each year (not limited to Nature Index journals).

Technical terms

Allotrope: A distinct crystallographic form of an element with a unique atomic arrangement.

Metastable phase: A non-equilibrium structure that persists at ambient conditions after high-pressure treatment.

Diamond cubic: The ambient-pressure lattice of silicon and germanium, characterised by tetrahedral bonding and semiconductor behaviour.

β-Sn phase: A high-pressure tetragonal form of silicon or germanium that serves as a precursor to denser polymorphs.

Shock compression: Rapid application of pressure via dynamic loading to induce phase transitions on ultrafast timescales.

Equation of state: A relationship describing the dependence of pressure, volume and temperature for a material.

Nucleation barrier: The energy threshold required to initiate the formation of a new phase during a transformation.

References

1. Atomistic deformation mechanism of silicon under laser-driven shock compression. Nature Communications (2022).
2. Experimental evidence of new tetragonal polymorphs of silicon formed through ultrafast laser-induced confined microexplosion. Nature Communications (2015).
3. Pressure-induced superconductivity in a novel germanium allotrope. Materials Today Physics (2024).
4. Unraveling the atomic-scale pathways driving pressure-induced phase transitions in silicon. Materials Today Nano (2025).
5. Formation of distinctive nanostructured metastable polymorphs mediated by kinetic transition pathways in germanium. Matter and Radiation at Extremes (2025).